Effect of Water Depth Change on Manning Coefficient for Partially-Filled Circular Culverts.

Document Type : Research Studies

Authors

1 Demonstrator, Civil Engineering Department, Higher Institute of Engineering and Technology, Kafr El-Sheikh, Egypt,

2 Lecturers, Irrigation and Hydraulics Engineering Department, Faculty of Engineering-Tanta University, Egypt,

3 Hydraulic Professor, is with Irrigation and Hydraulic Engineering Department, Faculty of Engineering, Tanta University, Tanta, Egypt

Abstract

Culvert is a structure used to convey surface runoff through embankments. The circular is the popular section for design pipes, such as culverts, drain tiles and sewers of small and medium sizes. Also it may be made of concrete, steel, corrugated metal and polyethylene. Manning's equation is most commonly used throughout the world for the purpose of computing flow velocities in open channel. Manning roughness coefficient is one of the effective factors on water velocity and discharge. The present study is about the determination of the relation between relative depth and relative roughness for circular culvert. For this purpose, field work was carried out on four pipe culverts on canals at El-Mahalla El kubra, Egypt. The culverts are of different diameters, slopes and materials. The velocity is recorded by using FlowTracker. Manning roughness coefficient greatly varied with the variation of relative depth, surface roughness and discharge. For four culverts, a total of 143 depth data points were collected at different discharges ranging from 0.004 to 4.750 m3/sec. New equations are developed for relation between the relative depth (d/D) and the relative roughness (n/nf) for flow depths less than 25% full for four pipe culverts on El Mahalla El Kubra, Egypt, when the water geometries are given. 

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